The problem of biofouling of membranes, pipes, cooling towers and other water-contacting surfaces is an ongoing problem in water-related processes and systems, and particularly in water desalination processes.
Development of biofouling on membrane surfaces presents one of the more serious problems in operating desalination plants based on reverse osmosis (RO) technology, especially for desalination of treated wastewater after secondary treatment.
The layer of biofouling on the membranes causes an increase in the input pressure, a decrease in product flow and an increase in the pressure drop on the surface of the membranes between the feed side and the concentration side. These changes cause a decrease in the production of the desalination facilities, an increase in energy consumption and a frequent need for chemical cleaning of the membranes in order to remove the biofouling layers.
The development of the biofouling results from adsorption and growth of microorganisms, found in the feed water, on the membrane surfaces.
Several methods are available for the prediction of biofouling, same are laboratory tests that include AOC (Assimilable Organic Carbon), BDOM (Biodegradable Dissolved Organic Matter) BOD (Biochemical Oxygen Demand), DOC (Dissolved Organic Carbon), TBC (Total Microorganisms Count), TOC (Total Organic Carbon). For field tests most of the measurements based on growing of biofilm on measuring surfaces. Several commercial biofilm identification kits are available, which detect presence of biofilm; the most common of these is the Biological Activity Reaction Test (BART) kit or the HydroBio Test kit.
Dyes for detecting microorganisms were also described. [Turner Nikki, W. E. Sandine, P. R. Elliker, and E. A. Day, “Use of Tetrazolium Dyes in an Agar Medium for Differentiation of Streptococcus Lactis and Streptococcus Cremoris”, Journal of Dairy Science, 46:380-385 (1963); Hayashi Shuhei, Takeshi Kobayashi, and Hiroyuki Honda, “Simple and rapid cell growth assay using tetrazolium violet coloring method for screening of organic solvent tolerant bacteria”, Journal of Bioscience and Bioengineering, 96(4):360-363 (2003)].